Crude oil produced from geological formations can contain various amounts of water. The water contents normally vary both between production wells and during the lifetime of one and the same production well. Water and crude oil are immiscible by nature and are normally in different phases in an oil-containing geological formation. However, as oil is produced, it is inevitable that at the same time water is also produced. As the crude oil and water are transported through production tubing and equipment, they are subject to significant mixing energy, especially at points of pressure release. This mixing energy together with naturally occurring emulsifying compounds in the crude oil can create quite persistent emulsions. The nature of these emulsions can vary widely depending on the composition of the crude oil, the production method, etc.
For economical and logistics reasons as well as demands from downstream operations (refineries, etc.) it is very important to separate water from the produced oil as rapidly and completely as possible already at the production site. This separation is severely hampered by the above-mentioned emulsification prior to the separation stage. Traditionally, both physical and chemical methods have been utilized to quickly break these emulsions in the separation equipment.
In a large majority of cases, the addition of organic chemicals (“demulsifiers”) is used either as the single method or in combination with physical methods. Demulsifiers can be used as a single compound, but due to the great variation in the nature of the water-in-crude oil emulsions, blends of demulsifiers are commonly utilized to achieve the highest possible technical efficiency in each single case.
Types of demulsifiers commonly used include mainly nonionic ethylene oxide/propylene oxide block polymers (polyglycols), alkylphenol-formaldehyde resin alkoxylates, and epoxy resin-based alkoxylates. (See “Something Old, Something New: A Discussion about Demulsifiers”, T. G. Balson, pp. 226-238, esp. pp 232-236 in Proceedings of the Chemistry in the Oil Industry VIII Symposium”, 3-5 Nov. 2003, Manchester, UK, published by The Royal Society of Chemistry, UK).
Some examples of patent publications relating to demulsifiers follow below.
U.S. Pat. No. 3,835,060 teaches that conventional demulsifiers include, e.g., polyoxyalkylene glycol and block polymers of polyoxyethylene-polyoxypropylene.
U.S. Pat. No. 5,401,439 discloses oil demulsifiers containing an alkoxylate of an alkylphenol-formaldehyde resin, an alcohol, a bisphenol or an amine, wherein the alkoxylate has a polydispersity of at least 1.7.
US 2004/0266973-A1 describes the use of an alkoxylated alkylphenol-arylaldehyde polymer for resolving water-in-oil emulsions, especially emulsions of water in crude oil, and US 2005/0080221-A1 describes the use of an alkoxylated alkylphenol-formaldehyde-diamine polymer for the same purpose.
U.S. Pat. No. 3,903,006 discloses a hydraulic pressure transmission fluid consisting of, or comprising, a synthetic orthoester. The orthoester is either the hydraulic pressure transmission fluid itself or, present in only minor amounts, as a water scavenger; i.e. it will remove minor amounts of water (moisture) present in the hydraulic fluid by participating in a chemical reaction with the water.
For a number of years there has been strong pressure for the use of more environmentally adapted chemicals in various application areas. This is also the case for oilfield production chemicals including demulsifiers, especially as regards their use in off-shore oil production. The presently used demulsifiers are for the most part biologically persistent, i.e. they exhibit a very poor biodegradability. Thus, there is a great need for new demulsifiers with an acceptable biodegradation profile combined with a low ecotoxicity and an excellent technical performance.
Thus, the aim of the present invention is to provide new efficient demulsifiers for breaking water-in-oil emulsions. In addition, said demulsifiers should also have an improved biodegradability profile compared to previously mentioned standard types of demulsifiers and exhibit a low ecotoxicity.
Now it has surprisingly been found that an orthoester based polymer having the general formula
wherein R1 is hydrogen or a hydrocarbyl group with 1-4 carbon atoms, R2, R3, and R4 are, independently, a group comprising C3-C4, preferably C3, alkyleneoxy groups and/or ethyleneoxy groups in any order, preferably in blocks, preferably with both ethyleneoxy groups and C3-C4 alkyleneoxy groups being present, and an end group Y, which is, independently, hydrogen, a hydrocarbyl group with 1-30, preferably 1-8, more preferably 1-6, and most preferably 1-4 carbon atoms, a group —(CH2)zNR5R6 or —(CH2)zN+R5R6R7, wherein each of R5, R6, and R7 is, independently, an alkyl group with 1-22 carbon atoms or —CH2CH2OH, and z is 2 or 3; the end group Y preferably being H or a hydrocarbyl group, provided that at least one of the groups R2, R3, and R4 comprises at least one block of at least on average 4 alkyleneoxy groups with 3 and/or 4 carbon atoms, and provided that if Y is hydrogen, then at least one ethyleneoxy or alkyleneoxy group is connected to Y; or a di- or polycondensate of the polymer via free hydroxyl groups in R2, R3 or R4, is an excellent demulsifier for water/oil emulsions, and at the same time has a better biodegradability than the prior art compounds.
In one embodiment R1 is hydrogen or a hydrocarbyl group with 1-4 carbon atoms, R2, R3, and R4 are, independently, a group -(A)n(CH2CH2O)mY or —(CH2CH2O)m(A)nY, wherein each A is, independently, an alkyleneoxy group with 3-4, preferably 3, carbon atoms, n and m are, on average and independently, a number of 0-100, preferably 1-100, more preferably 2-100, even more preferably 3-100, still more preferably 5-100, and most preferably 10-100, provided that at least one of the groups R2, R3, and R4 comprises at least one block of at least on average 4 alkyleneoxy groups with 3 and/or 4 carbon atoms, and each Y is, independently, hydrogen, a hydrocarbyl group with 1-30, preferably 1-8, more preferably 1-6, and most preferably 1-4 carbon atoms, a group —(CH2)zNR5R6 or —(CH2)zN+R5R6R7, wherein each of R5, R6, and R7 is, independently, an alkyl group with 1-22 carbon atoms or —CH2CH2OH, and z is 2 or 3; Y preferably is hydrogen or a hydrocarbyl group; provided that if Y is hydrogen, then at least one of n and m is a number of 1-100, or a di- or polycondensate of the polymer via free hydroxyl groups in R2, R3 or R4.
In another embodiment, the sum of all n in the polymer is 10-1200 and at least one of the groups R2, R3, and R4 comprises at least one block with 6-20 alkyleneoxy groups with 3-4 carbon atoms. The blocks containing alkyleneoxy groups with 4 carbon atoms can be made using either butylene oxide, in which case the blocks consist of branched alkyleneoxy groups, or polytetrahydrofuran, wherein the alkyleneoxy groups are linear. The blocks (A)n and (CH2CH2O)m can be added in any order, but preferably the (A)n block is closer to the orthoester bond than the (CH2CH2O)m block.
In still another embodiment, the orthoester based polymer for use as a demulsifier for water/oil emulsions is a product wherein R1 is hydrogen, (A)n is a block (CH2CH2CH2CH2O)n, Y is hydrogen, and m is at least 3; preferably, the ortho ester is a di- or polycondensate of the polymer via free hydroxyl groups in R2, R3 and R4.
The amount of ethyleneoxy groups in the orthoester based polymer preferably is 40-85%, more preferably 50-75%, by weight of the total molecular weight.
As a consequence of the synthesis route, each product manufactured will be a mixture of a lot of molecular species. This results in a very broad span of molecular weights, with the lowest weights being around 600, more preferably around 1,000, and the highest molecular weights being around 100,000.
The weight average molecular weight (Mw) of the polymer preferably is at least 1,500, more preferably at least 2,000, and at most 40,000, more preferably at most 30,000.
In one further embodiment, the orthoester based polymer for use as a demulsifier for water/oil emulsions is a product wherein R1 is hydrogen, A is an alkyleneoxy group with 3 carbon atoms, and Y is hydrogen, and wherein the amount of ethyleneoxy groups is 50-75% by weight of the total molecular weight, the molecular weight span is 1,000-100,000, and the weight average molecular weight (Mw) is 2,000-30,000.
The orthoester polymers (I) can be produced by reacting an orthoester of the general formula
wherein R1 has the same meaning as above and R8 is a hydrocarbyl group with 1-4 carbon atoms, in one or several steps, with reactants comprising C3-C4, preferably C3, alkyleneoxy groups and/or ethyleneoxy groups in any order, preferably in blocks, an end group Y, which is H or a hydrocarbyl group with 1-30 carbon atoms, and one hydroxyl group at the other end of the molecule, herein denoted as reactants having the formula HO(A)n(CH2CH2O)mY, and/or R5R6N(CH2)zOH or R5R6R7N+(CH2)zOH, wherein the symbols n, m, Y, z, R5, R6, and R7 have the same meaning as above. The reaction is performed under removal, preferably by evaporation, of liberated hydroxyl-containing compounds of the formula R8OH. As regards products (I) comprising the group —(CH2)zN+R5R6R7, these are preferably made by quaternizing an orthoester product comprising the group —(CH2)zNR5R6 with an alkylating agent R7-X, wherein R7 is a C1-C4 alkyl group and X is any conventional source for an anion of a quaternary ammonium compound, such as a halogen atom or OSO3CH3.
Because of the method used to produce the orthoester polymers, it should be realized that formula (I) only represents an average orthoester molecule and that specific individual species may have a structure deviating from formula I. For each starting orthoester molecule there are three positions that can be substituted by the reactants. If, e.g., 2 moles of HO(A)n(CH2CH2O)mY and 1 mole of R5R6N(CH2)zOH are added to the starting orthoester, this will result in some molecules wherein one of the R8 groups is replaced by -(A)n(CH2CH2O)mY and two of the R8 groups are replaced by —(CH2)zNR5R6, some molecules wherein two of the R8 groups are replaced by -(A)n(CH2CH2O)mY and one of the R8 groups is replaced by —(CH2)zNR5R6, some molecules wherein all three groups R8 are replaced by -(A)n(CH2CH2O)mY, and some molecules wherein all three groups R8 are replaced by —(CH2)zNR5R6. The product resulting from the reaction described above thus is a mixture of several components, but the average molecule will be an orthoester wherein two of the groups R8 have been replaced by -(A)n(CH2CH2O)mY and one of the groups R8 has been replaced by —(CH2)zNR5R6.
The above method has been described in detail in the patent publications EP-B 909 286, EP-B 1 042 266, and WO 03/018534. It is noted that the products of the present invention differ from the products described in the last publication in that the former must contain at least one block of at least on average 4 alkyleneoxy groups with 3 and/or 4 carbon atoms.
However, when an orthoester compound contains free hydroxyl groups, i.e. when Y is H, then several orthoester molecules may condensate into polymeric structures having higher molecular weights. In formula (I) the average individual orthoester compound is displayed, but formula (I) also symbolizes the polymeric structures that may result from the condensation of several orthoester molecules having free hydroxyl groups. An example of such a polymeric structure is shown below. Here five orthoester molecules have reacted together to form a polycondensate via free hydroxyl groups of the individual orthoester molecules. To obtain this structure, an orthoester of formula II can be reacted with a polypropylene glycol (PPG) and an alcohol ethoxylate of the formula RO(CH2CH2O)mH, wherein R is a hydrocarbyl group having 1-30 carbon atoms. The resulting polymer (III) can react further with more orthoester molecules, since there is still one terminal hydroxyl group left in the molecule. The symbols R1, R8, m, and n have the same meaning as stated above.

From the above it is evident that when an orthoester (II) is reacted with compounds having two hydroxyl groups, such as PPG or PEG, then two orthoester molecules of formula (II) may react with the same PPG or PEG molecule, and consequently the ratios between (II) and PPG or PEG can be varied within a wide range to yield products having widely different molecular weights. Further, it is possible to stop the reaction at a certain degree of condensation by discontinuing the heating and removal of R8OH, followed by neutralization of the acid catalyst.
Another possible route to obtaining products of formula (I) wherein Y is H and n and m are 1-100 is to react an orthoester of general formula (II) with a reactant having the formula HO(A)nY, wherein Y is hydrogen, and then to react the obtained intermediate with Σm moles of ethylene oxide. The latter reaction is preferably catalyzed by alkaline catalysts, preferably an alkali metal hydroxide such as NaOH or KOH, or an alkali metal alkoxide such as NaOCH3 or KOCH3. Since the orthoester will rearrange under acid conditions, the use of an acid catalyst is less preferred for the ethoxylation step. The ethoxylation reaction is performed in a manner which is well known in the art. It is also possible to react an orthoester of formula (II) with a reactant HO(CH2CH2O)mY, wherein Y is hydrogen, and then react the obtained intermediate with Σn moles of an alkylene oxide having 3-4 carbon atoms using alkaline catalysis. Also the conditions for performing such an alkoxylation reaction are well known to the man skilled in the art.
Wherever the degree of alkoxylation is discussed, the numbers referred to are molar average numbers. Consequently, all numbers m and n referred to above and henceforth, as well as the numbers o and p referred to below, are molar average numbers.
The ethoxylation of orthoesters not containing any hydroxyl groups has been disclosed in U.S. Pat. No. 2,867,667. In this method boron trifluoride is used as a catalyst, and the reaction is performed in the neighborhood of 0° C. or lower due to the sensitivity of the orthoester to the catalyst at higher temperatures.
Some of the orthoester based polymers are new, and the invention also relates to these compounds per se.
Thus the invention relates to an orthoester based polymer according to formula (I), wherein R1 is hydrogen or a hydrocarbyl group with 1-4 carbon atoms, R2 is a group comprising C3-C4, preferably C3, alkyleneoxy groups and/or ethyleneoxy groups in any order, preferably in blocks, and an end group Y, which is H or a hydrocarbyl group with 1-4 carbon atoms, R4 is a group -(A)o(CH2CH2O)pZ or —(CH2CH2O)p(A)oZ, wherein Z is a hydrocarbyl group with 5-30 carbon atoms, each A is, independently, an alkyleneoxy group with 3-4 carbon atoms, o is a number of 0-100, preferably 0-5, and p is on average a number of at least 1, preferably of at least 5, and of at most 100, preferably of at most 20, or a group —(CH2)zNR5R6 or —(CH2)zN+R5R6R7, wherein R5, R6, and R7 are, independently, an alkyl group with 1-22 carbon atoms or —CH2CH2OH and z is 2 or 3, and R3 is selected from the group R2, R4, and a hydrocarbyl group with 1-4 carbon atoms, and provided that at least one of the groups R2, R3, and R4 comprises at least one block of at least 4 alkyleneoxy groups with 3 and/or 4 carbon atoms, or a di- or polycondensate of the polymer via free hydroxyl groups in R2 or R3.
A method for producing a polymer or polymer mixture as defined above comprising one or several steps is performed by reacting an orthoester having general formula (II), wherein R1 has the same meaning as above and R8 is a hydrocarbyl group with 1 to 4 carbon atoms, with reactants comprising C3-C4, preferably C3, alkyleneoxy groups and/or ethyleneoxy groups in any order, preferably in blocks, an end group Y, which is H or a hydrocarbyl group with 1-4 carbon atoms, and one hydroxyl group at the other end of the molecule, HO(A)o(CH2CH2O)pZ, HO(CH2CH2O)p(A)oZ, wherein A, 0, p, and Z have the same meaning as above, and R5R6N(CH2)zOH or R5R6R7N+(CH2)zOH, wherein the symbols z, R5, R6, and R7 have the same meaning as above, under removal of liberated hydroxyl-containing compounds of the formula R8OH, or alternatively, to obtain an orthoester based polymer wherein R4 is a group —(CH2)zN+R5R6R7, by quaternizing an orthoester based polymer wherein R4 is —(CH2)zNR5R6 with an alkylating agent R7X, wherein R7 is a C1-C4 alkyl group and X is a conventional source for an anion of a quaternary ammonium compound, such as a halogen atom or OSO3CH3.
More specifically, the invention relates to an orthoester based polymer according to formula (I), wherein R1 is hydrogen or a hydrocarbyl group with 1-4 carbon atoms, R2 is a group -(A)n(CH2CH2O)mY or —(CH2CH2O)m(A)nY, wherein each A is an alkyleneoxy group with 3-4 carbon atoms, n and m are, on average and independently, a number of 0-100, Y is H or a hydrocarbyl group with 1-4 carbon atoms, provided that if Y is hydrogen, then at least one of n or m in the same substituent as said Y is a number of 1-100 for that group, R4 is a group -(A)o(CH2CH2O)pZ or —(CH2CH2O)p(A)oZ, wherein Z is a hydrocarbyl group with 5-30 carbon atoms, o is a number of 0-100, preferably 0-5, and p is on average a number of at least 1, preferably of at least 5, and of at most 100, preferably of at most 20, or a group —(CH2)zNR5R6 or —(CH2)zN+R5R6R7, wherein R5, R6, and R7 are, independently, an alkyl group with 1-22 carbon atoms or CH2CH2OH and z is 2 or 3, and R3 is selected from the group R2, R4, and a hydrocarbyl group with 1-4 carbon atoms, and provided that at least one of the groups R2, R3, and R4 comprises at least one block of at least 4 alkyleneoxy groups with 3 and/or 4 carbon atoms, or a di- or polycondensate of the polymer via free hydroxyl groups in R2 or R3.
A method for producing a polymer or polymer mixture as defined above comprising one or several steps is performed by reacting an orthoester having the general formula (II), wherein R1 has the same meaning as above and R8 is a hydrocarbyl group with 1 to 4 carbon atoms, with reactants selected from the group having the formulae HO(A)n(CH2CH2O)mY, HO(CH2CH2O)m(A)nY, wherein A, n, m, and Y have the same meaning as above, HO(A)o(CH2CH2O)pZ or HO(CH2CH2O)p(A)oZ, wherein A, o, p, and Z have the same meaning as above, and R5R6N(CH2)zOH or R5R6R7N+(CH2)zOH, wherein the symbols z, R5, R6, and R7 have the same meaning as above, under removal of liberated hydroxyl-containing compounds of the formula R8OH, or alternatively, to obtain an orthoester based polymer wherein R4 is a group —(CH2)zN+R5R6R7, by quaternizing an orthoester based polymer wherein R4 is —(CH2)zNR5R6 with an alkylating agent R7X, wherein R7 is a C1-C4 alkyl group and X is a conventional source for an anion of a quaternary ammonium compound, such as a halogen atom or OSO3CH3.
One of the preferred new products of the invention is an orthoester based polymer according to formula (I), wherein R1 is hydrogen or a hydrocarbyl group with 1-4 carbon atoms, R2 is a group -(A)n(CH2CH2O)mY or —(CH2CH2O)m(A)nY, wherein each A is an alkyleneoxy group with 3-4 carbon atoms, n and m are a number of 0-100, Y is H or a hydrocarbyl group with 1-4 carbon atoms, provided that if Y is hydrogen, then at least one of n or m in the same substituent as said Y is a number of 1-100 for that group, R4 is a group -(A)o(CH2CH2O)pZ or —(CH2CH2O)p(A)oZ, wherein Z is a hydrocarbyl group with 5-30 carbon atoms, o is on average a number of 0-100, preferably 0-5, and p is on average a number of at least 1, preferably of at least 5, and of at most 100, preferably of at most 20, and R3 is selected from the group R2, R4, and a hydrocarbyl group with 1-4 carbon atoms, and provided that at least one of the groups R2, R3, and R4 comprises at least one block of at least 4 alkyleneoxy groups with 3 and/or 4 carbon atoms, or a di- or polycondensate of the polymer via free hydroxyl groups in R2 or R3.
A method for producing a polymer or polymer mixture as defined for the preferred product above, comprising one or several steps, is performed by reacting an orthoester having general formula (II), wherein R1 has the same meaning as stated earlier and R8 is a hydrocarbyl group with 1 to 4 carbon atoms, with reactants having the formulae HO(A)n(CH2CH2O)mY or HO(CH2CH2O)m(A)nY and HO(A)o(CH2CH2O)pZ or HO(CH2CH2O)p(A)oZ, wherein A, n, m, Y, o, p, and Z have the same meaning as above, under removal, preferably by evaporation, of liberated hydroxyl-containing compounds of the formula R8OH.
Another preferred new product of the invention is an orthoester based polymer according to formula (I), wherein R1 is hydrogen or a hydrocarbyl group with 1-4 carbon atoms, R2 is a group -(A)n(CH2CH2O)mY or —(CH2CH2O)m(A)nY, wherein each A is an alkyleneoxy group with 3-4 carbon atoms, n and m are a number of 0-100, Y is H or a hydrocarbyl group with 1-4 carbon atoms, provided that when Y is hydrogen, at least one of n or m is a number of 1-100 for that group, R4 is a group —(CH2)zNR5R6 or —(CH2)zN+R5R6R7, wherein R5, R6, and R7 are, independently, an alkyl group with 1-22 carbon atoms or —CH2CH2OH and z is 2 or 3, and R3 is selected from the group R2, R4, and a hydrocarbyl group with 1-4 carbon atoms, and provided that at least one of the groups R2, R3, and R4 comprises at least one block of at least 4 alkyleneoxy groups with 3 and/or 4 carbon atoms, or a di- or polycondensate of the polymer via free hydroxyl groups in R2 or R3.
A method for producing a polymer or polymer mixture as defined for the preferred product above, comprising one or several steps, is performed by reacting an orthoester having general formula (II), wherein R1 has the same meaning as stated earlier and R8 is a hydrocarbyl group with 1 to 4 carbon atoms, with reactants having the formulae R5R6N(CH2)zOH or R5R6R7N+(CH2)zOH and HO(A)n(CH2CH2O)mY or HO(CH2CH2O)m(A)nY, wherein the symbols n, m, Y, z, R5, R6, and R7 have the same meaning as above, under removal, preferably by evaporation, of liberated hydroxyl-containing compounds of the formula R8OH, or alternatively, to obtain an orthoester based polymer wherein R4 is a group —(CH2)zN+R5R6R7, preferably an orthoester polymer wherein R4 is —(CH2)zNR5R6 is quaternized by an alkylating agent R7X, wherein R7 is a C1-C4 alkyl group and X is a halogen atom or OSO3CH3, preferably a halogen atom. The most preferred alkylating agents are methyl chloride and dimethyl sulfate.
Suitable starting materials HO(A)n(CH2CH2O)mY, wherein Y is H, are polyethylene glycols (PEG), polypropylene glycols (PPG), polybutylene glycols, polytetrahydrofurans, block or random copolymers of ethylene oxide and propylene oxide, or of ethylene oxide and butylene oxide, and ethoxylated polytetrahydrofurans. Suitable starting materials wherein Y is an alkyl group are poly(ethylene glycol) monomethyl ether, poly(ethylene glycol) monoethyl ether, poly(ethylene glycol) monopropyl ether, poly(ethylene glycol) monobutyl ether, diethylene glycol monobutyl ether, and ethoxylated alcohols, such as ethoxylated n-hexanol, n-octanol, 2-ethylhexanol, nonanol, n-decyl alcohol, 2-propylheptanol, n-dodecyl alcohol, tridecyl alcohol, C10-C12-alkyl alcohol, C9-C11-alkyl alcohol, or C16-C18-alkyl alcohol. Suitable starting materials wherein Y is a group —(CH2)zNR5R6 are 2-(dimethylamino)ethanol, 3-dimethylamino-1-propanol, 2-(diethylamino)ethanol, 3-diethylamino-1-propanol, 2-(diisopropylamino)ethanol, 2-(dibutylamino)ethanol, and primary alkylamines ethoxylated with two moles of ethylene oxide (EO), such as n-hexyl amine+2EO, 2-ethylhexyl amine+2EO, 2-propylheptyl amine+2EO, n-decyl amine+2EO, n-dodecyl amine+2EO, (coco alkyl)amine+2EO, n-tetradecyl amine+2EO, n-hexadecyl amine+2EO, n-octadecyl amine+2EO, oleyl amine+2EO, (tallow alkyl)amine+2EO, (rape seed alkyl)amine+2EO, (soya alkyl)amine+2EO, and erucyl amine+2EO.
The orthoester polymer can be used as a demulsifier for separating water/oil emulsions in the production of oil. The polymer can also be used as a demulsifier in a fermentation process, e.g. in the production of penicillin. In this production process an extraction is performed which gives rise to a persistent o/w emulsion, which breaks when the demulsifiers according to the present invention are added. The demulsifiers according to the invention may be used in any process where a water/oil emulsion is formed, and their use is not restricted to the applications mentioned above, By the term water/oil emulsion is meant here any emulsion between water and oil, i.e. both w/o and o/w are included. It is noted that the water/oil emulsions that are demulsified are not hydraulic pressure transmission fluids.
The demulsifier can be combined with solvents and other chemicals typically used in these applications, and consequently it can be used either as such or in a formulation. The amount of water present in the w/o emulsion to be demulsified may range from 0.5 to 98%, based on the total amount of w/o emulsion. Preferably, at least 1% water is present in the emulsion, more preferably at least 2%, even more preferably at least 3%, still more preferably at least 4%, and most preferably at least 5% is present.
A common way to characterize demulsifiers is by their relative solubility number (RSN value). The test is carried out by dissolving a specific amount of demulsifier in a defined volume of an organic solvent mixture and then titrating this solution with water. Once a certain volume of water has been added, the solution will turn from clear (transparent) to cloudy. The water volume (in mL) at which this change takes place is the RSN value. Ordinarily, more hydrophilic (water-soluble) demulsifiers have a higher RSN value than more hydrophobic (oil-soluble) ones. For a very large majority of commercially used demulsifiers, the RSN value found is in the range of 5-25. For the specific solvent mixture and test conditions used to characterize the products of the present invention, see the experimental section.
The composition of crude oils (and production water) can differ considerably between different wells and even, with time, for the same well. This means that the composition of demulsifiers has to be especially adapted for each well and stage of production to give a good performance. The demulsifiers should fulfill four main performance criteria, rapid separation of the oil-and-water phase, creation of a distinct interface, giving low residual water contents in the separated oil phase, and giving a good quality of the separated water phase. The last demand is important in order to minimize pollution by discharged water and/or the need for further water treatment before discharge. To a person skilled in surface chemistry, it will be obvious that it is very difficult to find single molecules that fulfill all four of these demands. For this reason blends of demulsifiers are very commonly used in practice to get optimal results. Often demulsifiers with both comparatively high and comparatively low RSN values are used in the optimized blend. Thus, it is very valuable if the same type of basic chemistry can be utilized to produce demulsifiers with both high and low RSN values. It is demonstrated in the examples that a wide variety of RSN values can be achieved with the types of compounds of the present invention.
When used for separation of the water/oil emulsions that result from a process for the production of oil, an orthoester polymer demulsifier according to the present invention may be applied at the well head, at a suitable injection point downstream, or at any stage of crude oil processing. A suitable amount of orthoester polymer added to the oil or emulsion can for example be from 1 to 500 mg/kg (mg/kg=ppm by weight, ppmw), normally from 1 to 50 mg/kg, calculated on the amount of water and oil. The exact amount of demulsifier is dependent on the type of oil, some oils requiring more and others requiring less demulsifier. Mixtures of demulsifiers according to the invention can be used, but also one or more demulsifiers according to the invention can be used together with one or more conventional demulsifiers. For other applications, such as for breaking emulsions arising in fermentation processes, larger amounts of demulsifier may be needed, e.g. up to 0.5% based on the total amount of broth.
The present invention is further illustrated by the following examples.